localharness 0.76.0

//! Browser OPFS-backed implementation of [`Filesystem`].
//!
//! Uses the Origin Private File System exposed via
//! `navigator.storage.getDirectory()`. Each browser tab/origin gets its
//! own private root directory.
//!
//! ## Atomicity
//!
//! `write_atomic` relies on OPFS's `FileSystemWritableFileStream`
//! semantics: writes are buffered to a swap file and the original is
//! atomically replaced on `close()`. A page reload mid-write leaves
//! the original file intact.
//!
//! ## Path handling
//!
//! OPFS has no native path syntax — only handles. This impl splits
//! incoming paths on `/`, drops empty components, and resolves each
//! component as a directory (or final file). Leading slashes are
//! ignored; OPFS-rooted paths and relative paths are equivalent.

use std::cell::{Cell, RefCell};
use std::collections::HashMap;
use std::rc::Rc;

use async_trait::async_trait;
use js_sys::{Function, Object, Promise, Reflect, Uint8Array};
use wasm_bindgen::prelude::*;
use wasm_bindgen::JsCast;
use wasm_bindgen_futures::JsFuture;
use web_sys::{
    File, FileSystemDirectoryHandle, FileSystemFileHandle, FileSystemGetDirectoryOptions,
    FileSystemGetFileOptions, FileSystemHandle, FileSystemHandleKind, FileSystemRemoveOptions,
    FileSystemWritableFileStream, MessageEvent, Worker,
};

use super::{DirEntry, EntryKind, Filesystem, Metadata, WalkEntry};
use crate::error::{Error, Result};

/// Wall-clock bound on a single OPFS write (either path). The 2026-06-18 iOS
/// gate existed because a WebKit write stalled FOREVER and froze the
/// single-thread wasm app mid-onboarding — a pathological engine must surface
/// as an ERROR the UI can show, never an infinite hang.
const WRITE_TIMEOUT_MS: u32 = 15_000;

/// Hard cap on entries a single `walk` collects. find_file/search_directory
/// cap their own RESULTS, but they collect the whole walk first, so without
/// this a walk over a huge tree would exhaust memory. Mirrors
/// `NativeFilesystem::MAX_WALK_ENTRIES`; 200k is far beyond any real workspace.
const MAX_WALK_ENTRIES: usize = 200_000;

/// Filesystem backed by the browser's Origin Private File System.
///
/// Cheap to clone: holds an `Rc` to the OPFS root handle once acquired.
#[derive(Debug, Clone, Default)]
pub struct OpfsFilesystem {
    // Cache the OPFS root after first acquisition; getDirectory()
    // returns the same logical handle every time but each call is async.
    root: Rc<RefCell<Option<FileSystemDirectoryHandle>>>,
}

impl OpfsFilesystem {
    pub fn new() -> Self {
        Self::default()
    }

    async fn root_handle(&self) -> Result<FileSystemDirectoryHandle> {
        // NEVER hold a `Ref`/`RefMut` across the `getDirectory().await` below.
        // The single-threaded wasm executor interleaves tasks at await points,
        // and on iOS WebKit's microtask timing a borrow held across an await can
        // be re-entered by a concurrent OPFS op → "RefCell already borrowed".
        // Take an OWNED clone out of the borrow in its own statement, so the
        // guard is dropped before we await.
        let cached = self.root.borrow().clone();
        if let Some(h) = cached {
            return Ok(h);
        }
        let window = web_sys::window()
            .ok_or_else(|| Error::fs("getDirectory", "", "no window: not in a browser"))?;
        let storage = window.navigator().storage();
        let promise = storage.get_directory();
        let val = JsFuture::from(promise)
            .await
            .map_err(|e| Error::fs("getDirectory", "", format!("getDirectory: {}", js_err(&e))))?;
        let handle: FileSystemDirectoryHandle = val
            .dyn_into()
            .map_err(|_| {
                Error::fs("getDirectory", "", "getDirectory: not a FileSystemDirectoryHandle")
            })?;
        // Cache in a brief, await-free borrow. Two concurrent first-init callers
        // each resolve their own `getDirectory()` (OPFS returns the same logical
        // root every time), so a double-init just caches the equivalent handle
        // twice — harmless, never a borrow conflict.
        *self.root.borrow_mut() = Some(handle.clone());
        Ok(handle)
    }

    /// Walk a path's parent components, returning the deepest directory
    /// handle and the final segment (`None` if the path resolves to the
    /// root itself).
    async fn resolve_parent(
        &self,
        path: &str,
        create_dirs: bool,
    ) -> Result<(FileSystemDirectoryHandle, Option<String>)> {
        let parts = split_path(path);
        if parts.is_empty() {
            return Ok((self.root_handle().await?, None));
        }
        let mut dir = self.root_handle().await?;
        for component in &parts[..parts.len() - 1] {
            dir = get_subdir(&dir, component, create_dirs).await?;
        }
        Ok((dir, Some(parts.last().unwrap().clone())))
    }

    /// Resolve a path to the directory handle it names (errors if the
    /// path doesn't exist or names a file).
    async fn resolve_dir(&self, path: &str) -> Result<FileSystemDirectoryHandle> {
        let parts = split_path(path);
        let mut dir = self.root_handle().await?;
        for component in &parts {
            dir = get_subdir(&dir, component, false).await?;
        }
        Ok(dir)
    }

    /// The main-thread `FileSystemWritableFileStream` write (non-WebKit
    /// engines, and the fallback when the broker is unsupported). Callers wrap
    /// it in [`bounded`] — never call it bare from the trait surface.
    async fn write_atomic_stream(&self, path: &str, bytes: &[u8]) -> Result<()> {
        let (parent, name) = self.resolve_parent(path, true).await?;
        let name = name.ok_or_else(|| {
            Error::fs("write_atomic", path, format!("write_atomic({path}): path is empty"))
        })?;
        let file_handle = get_file(&parent, &name, true).await?;
        let writable_val = JsFuture::from(file_handle.create_writable())
            .await
            .map_err(|e| {
                Error::fs("createWritable", path, format!("createWritable({path}): {}", js_err(&e)))
            })?;
        let writable: FileSystemWritableFileStream = writable_val
            .dyn_into()
            .map_err(|_| Error::fs("createWritable", path, "createWritable: not a writable stream"))?;
        // `Uint8Array::from(&[u8])` COPIES into a fresh standalone buffer
        // (byteOffset 0, length == payload). Never "optimize" this to
        // `Uint8Array::view` of wasm memory: WebKit bug 302733 (open through
        // Safari 26.4) ignores a view's byteOffset and writes the ENTIRE
        // underlying ArrayBuffer — for a wasm-memory view, the whole heap.
        let array = Uint8Array::from(bytes);
        let write_promise = writable
            .write_with_buffer_source(&array)
            .map_err(|e| Error::fs("write", path, format!("write({path}): {}", js_err(&e))))?;
        JsFuture::from(write_promise)
            .await
            .map_err(|e| Error::fs("write", path, format!("write({path}): {}", js_err(&e))))?;
        JsFuture::from(writable.close())
            .await
            .map_err(|e| Error::fs("close", path, format!("close({path}): {}", js_err(&e))))?;
        Ok(())
    }
}

/// Race `fut` against a wall-clock deadline. On timeout the abandoned future
/// is dropped mid-flight (its JS promise may still settle later — harmless);
/// the caller gets a typed error instead of a frozen app.
async fn bounded(
    ms: u32,
    op: &'static str,
    path: &str,
    fut: impl std::future::Future<Output = Result<()>>,
) -> Result<()> {
    use futures_util::future::{select, Either};
    match select(Box::pin(fut), Box::pin(crate::runtime::sleep_ms(ms))).await {
        Either::Left((res, _)) => res,
        Either::Right(((), _)) => Err(Error::fs(
            op,
            path,
            format!("{op}({path}): timed out after {ms}ms (engine OPFS stall) — data NOT saved"),
        )),
    }
}

// ---- WebKit write broker (the iOS fix) --------------------------------------
// web/opfs-worker.js performs writes via the worker-only
// `createSyncAccessHandle` (iOS 15.2+). The client here is feature-detected
// end-to-end: a spawn failure or an `unsupported` reply latches the broker
// DEAD and every write falls back to the bounded main-thread stream.

thread_local! {
    static BROKER: RefCell<Option<Broker>> = const { RefCell::new(None) };
    /// Sticky "stop trying the worker" latch (spawn failed / no sync API).
    static BROKER_DEAD: Cell<bool> = const { Cell::new(false) };
}

struct Broker {
    worker: Worker,
    /// id → the pending write's Promise `resolve`. Only ever borrowed in
    /// straight-line code — NEVER across an await (the RefCell-across-await
    /// iOS panic class; see `root_handle`).
    pending: Rc<RefCell<HashMap<u32, Function>>>,
    next_id: Cell<u32>,
    _onmessage: Closure<dyn FnMut(MessageEvent)>,
}

enum BrokerWrite {
    Done(Result<()>),
    /// This engine can't broker (no worker / no sync-access API) — caller
    /// falls through to the main-thread path. Latched, so it costs once.
    Unsupported,
}

/// WebKit detection: `navigator.vendor` is "Apple Computer, Inc." on Safari
/// AND every iOS browser shell (CriOS/FxiOS — WebKit is mandatory outside the
/// EU). `window.LH_FORCE_WORKER_FS = 1` forces the broker on any engine so
/// E2E can exercise it under Chromium (which has OPFS in automation).
fn engine_prefers_broker() -> bool {
    if BROKER_DEAD.with(Cell::get) {
        return false;
    }
    let Some(win) = web_sys::window() else { return false };
    if Reflect::get(&win, &JsValue::from_str("LH_FORCE_WORKER_FS"))
        .map(|v| v.is_truthy())
        .unwrap_or(false)
    {
        return true;
    }
    // `navigator.vendor` via Reflect (web-sys doesn't bind it): "Apple
    // Computer, Inc." on every WebKit shell; "Google Inc." on Chromium.
    Reflect::get(&win.navigator(), &JsValue::from_str("vendor"))
        .ok()
        .and_then(|v| v.as_string())
        .is_some_and(|v| v.starts_with("Apple"))
}

fn broker_spawn() -> Option<Broker> {
    let worker = Worker::new("/opfs-worker.js").ok()?;
    let pending: Rc<RefCell<HashMap<u32, Function>>> = Rc::new(RefCell::new(HashMap::new()));
    let map = Rc::clone(&pending);
    let onmessage = Closure::<dyn FnMut(MessageEvent)>::new(move |e: MessageEvent| {
        let data = e.data();
        let id = Reflect::get(&data, &JsValue::from_str("id"))
            .ok()
            .and_then(|v| v.as_f64())
            .unwrap_or(-1.0) as u32;
        let resolve = map.borrow_mut().remove(&id);
        if let Some(resolve) = resolve {
            let _ = resolve.call1(&JsValue::NULL, &data);
        }
    });
    worker.set_onmessage(Some(onmessage.as_ref().unchecked_ref()));
    Some(Broker { worker, pending, next_id: Cell::new(1), _onmessage: onmessage })
}

async fn broker_write(path: &str, bytes: &[u8]) -> BrokerWrite {
    // All setup is SYNCHRONOUS (spawn-if-needed, stash resolve, postMessage);
    // the only await is on the reply promise, outside every borrow.
    let fut = BROKER.with(|slot| {
        let mut slot = slot.borrow_mut();
        if slot.is_none() {
            *slot = broker_spawn();
        }
        let b = slot.as_ref()?;
        let id = b.next_id.get();
        b.next_id.set(id.wrapping_add(1));
        let pending = Rc::clone(&b.pending);
        let promise = Promise::new(&mut |resolve, _reject| {
            pending.borrow_mut().insert(id, resolve);
        });
        let msg = Object::new();
        let _ = Reflect::set(&msg, &JsValue::from_str("id"), &JsValue::from_f64(id as f64));
        let _ = Reflect::set(&msg, &JsValue::from_str("path"), &JsValue::from_str(path));
        // Fresh copy (byteOffset 0) — same bug-302733 rule as the stream path.
        let _ = Reflect::set(&msg, &JsValue::from_str("bytes"), &Uint8Array::from(bytes).buffer());
        if b.worker.post_message(&msg).is_err() {
            b.pending.borrow_mut().remove(&id);
            return None;
        }
        Some(JsFuture::from(promise))
    });
    let Some(fut) = fut else {
        BROKER_DEAD.with(|d| d.set(true));
        return BrokerWrite::Unsupported;
    };
    use futures_util::future::{select, Either};
    let reply = match select(Box::pin(fut), Box::pin(crate::runtime::sleep_ms(WRITE_TIMEOUT_MS)))
        .await
    {
        Either::Left((Ok(v), _)) => v,
        Either::Left((Err(e), _)) => {
            return BrokerWrite::Done(Err(Error::fs(
                "write_atomic",
                path,
                format!("write broker({path}): {}", js_err(&e)),
            )));
        }
        // Timed out: do NOT fall back (a late-settling worker write racing a
        // fallback write to the same file could corrupt it) and do NOT latch
        // (a slow-but-alive device shouldn't lose the broker forever).
        Either::Right(((), _)) => {
            return BrokerWrite::Done(Err(Error::fs(
                "write_atomic",
                path,
                format!("write broker({path}): timed out after {WRITE_TIMEOUT_MS}ms — data NOT saved"),
            )));
        }
    };
    let get = |k: &str| Reflect::get(&reply, &JsValue::from_str(k)).ok();
    if get("ok").and_then(|v| v.as_bool()) == Some(true) {
        return BrokerWrite::Done(Ok(()));
    }
    if get("unsupported").and_then(|v| v.as_bool()) == Some(true) {
        // No sync-access on this engine — latch + fall back (nothing was
        // written; the worker failed BEFORE touching the file).
        BROKER_DEAD.with(|d| d.set(true));
        return BrokerWrite::Unsupported;
    }
    let err = get("err").and_then(|v| v.as_string()).unwrap_or_else(|| "unknown".into());
    BrokerWrite::Done(Err(Error::fs("write_atomic", path, format!("write broker({path}): {err}"))))
}

#[async_trait(?Send)]
impl Filesystem for OpfsFilesystem {
    async fn read(&self, path: &str) -> Result<Vec<u8>> {
        let (parent, name) = self.resolve_parent(path, false).await?;
        let name =
            name.ok_or_else(|| Error::fs("read", path, format!("read({path}): path is empty")))?;
        let file_handle = get_file(&parent, &name, false).await?;
        let file_val = JsFuture::from(file_handle.get_file())
            .await
            .map_err(|e| Error::fs("getFile", path, format!("getFile({path}): {}", js_err(&e))))?;
        let file: File = file_val
            .dyn_into()
            .map_err(|_| Error::fs("getFile", path, format!("getFile({path}): not a File")))?;
        let buf = JsFuture::from(file.array_buffer())
            .await
            .map_err(|e| {
                Error::fs("arrayBuffer", path, format!("arrayBuffer({path}): {}", js_err(&e)))
            })?;
        let array = Uint8Array::new(&buf);
        Ok(array.to_vec())
    }

    async fn write_atomic(&self, path: &str, bytes: &[u8]) -> Result<()> {
        // WebKit engines (Safari, and EVERY iOS browser — CriOS/Firefox-iOS are
        // WebKit shells) broker writes through web/opfs-worker.js: Safari had
        // NO `createWritable` until Safari 26 (undefined on iOS ≤ 18 — the
        // 2026-06-18 "not available on iOS" gate), while the worker-only
        // `createSyncAccessHandle` has worked since iOS 15.2. One brokered
        // path covers iOS 15.2→26.x; `Unsupported` falls through to the
        // (timeout-bounded) main-thread stream below.
        if engine_prefers_broker() {
            match broker_write(path, bytes).await {
                BrokerWrite::Done(res) => return res,
                BrokerWrite::Unsupported => {}
            }
        }
        bounded(WRITE_TIMEOUT_MS, "write_atomic", path, self.write_atomic_stream(path, bytes))
            .await
    }

    async fn metadata(&self, path: &str) -> Result<Option<Metadata>> {
        let (parent, name) = self.resolve_parent(path, false).await?;
        let Some(name) = name else {
            // Path resolved to OPFS root — it's a directory.
            return Ok(Some(Metadata {
                kind: EntryKind::Directory,
                size: 0,
            }));
        };
        // Try file first, then directory.
        match get_file(&parent, &name, false).await {
            Ok(fh) => {
                let file_val = JsFuture::from(fh.get_file())
                    .await
                    .map_err(|e| Error::fs("getFile", path, format!("getFile({path}): {}", js_err(&e))))?;
                let file: File = file_val
                    .dyn_into()
                    .map_err(|_| Error::fs("getFile", path, format!("getFile({path}): not a File")))?;
                Ok(Some(Metadata {
                    kind: EntryKind::File,
                    size: file.size() as u64,
                }))
            }
            Err(_) => match get_subdir(&parent, &name, false).await {
                Ok(_) => Ok(Some(Metadata {
                    kind: EntryKind::Directory,
                    size: 0,
                })),
                Err(_) => Ok(None),
            },
        }
    }

    async fn read_dir(&self, path: &str) -> Result<Vec<DirEntry>> {
        let dir = self.resolve_dir(path).await?;
        let mut entries = collect_entries(&dir).await?;
        entries.sort_by(|a, b| a.name.cmp(&b.name));
        Ok(entries)
    }

    async fn walk(&self, path: &str, max_depth: Option<usize>) -> Result<Vec<WalkEntry>> {
        let root = self.resolve_dir(path).await?;
        let mut out = Vec::new();
        // Root entry itself at depth 0.
        out.push(WalkEntry {
            path: path.trim_end_matches('/').to_string(),
            kind: EntryKind::Directory,
            size: None,
        });
        walk_dir(&root, path, 1, max_depth, &mut out).await?;
        Ok(out)
    }

    async fn delete(&self, path: &str) -> Result<()> {
        let (parent, name) = self.resolve_parent(path, false).await?;
        let name =
            name.ok_or_else(|| {
                Error::fs("delete", path, format!("delete({path}): cannot delete OPFS root"))
            })?;
        let opts = FileSystemRemoveOptions::new();
        opts.set_recursive(true);
        let promise = parent.remove_entry_with_options(&name, &opts);
        JsFuture::from(promise)
            .await
            .map_err(|e| {
                Error::fs("removeEntry", path, format!("removeEntry({path}): {}", js_err(&e)))
            })?;
        Ok(())
    }
}

fn split_path(path: &str) -> Vec<String> {
    path.split('/')
        .filter(|s| !s.is_empty() && *s != ".")
        .map(|s| s.to_string())
        .collect()
}

async fn get_subdir(
    parent: &FileSystemDirectoryHandle,
    name: &str,
    create: bool,
) -> Result<FileSystemDirectoryHandle> {
    let opts = FileSystemGetDirectoryOptions::new();
    opts.set_create(create);
    let promise = parent.get_directory_handle_with_options(name, &opts);
    let val = JsFuture::from(promise)
        .await
        .map_err(|e| {
            Error::fs(
                "getDirectoryHandle",
                name,
                format!("getDirectoryHandle({name}): {}", js_err(&e)),
            )
        })?;
    val.dyn_into().map_err(|_| {
        Error::fs("getDirectoryHandle", name, format!("getDirectoryHandle({name}): wrong type"))
    })
}

async fn get_file(
    parent: &FileSystemDirectoryHandle,
    name: &str,
    create: bool,
) -> Result<FileSystemFileHandle> {
    let opts = FileSystemGetFileOptions::new();
    opts.set_create(create);
    let promise = parent.get_file_handle_with_options(name, &opts);
    let val = JsFuture::from(promise)
        .await
        .map_err(|e| {
            Error::fs("getFileHandle", name, format!("getFileHandle({name}): {}", js_err(&e)))
        })?;
    val.dyn_into()
        .map_err(|_| Error::fs("getFileHandle", name, format!("getFileHandle({name}): wrong type")))
}

/// Iterate a directory's entries via the JS async iterator protocol.
async fn collect_entries(dir: &FileSystemDirectoryHandle) -> Result<Vec<DirEntry>> {
    let iter_method =
        Reflect::get(dir, &JsValue::from_str("entries"))
            .map_err(|_| Error::fs("entries", "", "entries"))?;
    let iter_fn = iter_method
        .dyn_ref::<js_sys::Function>()
        .ok_or_else(|| Error::fs("entries", "", "entries() not callable"))?;
    let iterator = iter_fn
        .call0(dir)
        .map_err(|e| Error::fs("entries", "", format!("entries(): {}", js_err(&e))))?;
    let next_fn = Reflect::get(&iterator, &JsValue::from_str("next"))
        .map_err(|_| Error::fs("iterator.next", "", "iterator.next"))?
        .dyn_into::<js_sys::Function>()
        .map_err(|_| Error::fs("iterator.next", "", "iterator.next not a function"))?;

    let mut out = Vec::new();
    loop {
        let promise = next_fn
            .call0(&iterator)
            .map_err(|e| Error::fs("iterator.next", "", format!("iterator.next: {}", js_err(&e))))?;
        let result = JsFuture::from(js_sys::Promise::from(promise))
            .await
            .map_err(|e| {
                Error::fs("iterator await", "", format!("iterator await: {}", js_err(&e)))
            })?;
        let done = Reflect::get(&result, &JsValue::from_str("done"))
            .ok()
            .and_then(|v| v.as_bool())
            .unwrap_or(true);
        if done {
            break;
        }
        let value = Reflect::get(&result, &JsValue::from_str("value"))
            .map_err(|_| Error::fs("iterator value", "", "iterator value"))?;
        // value is [name, handle] tuple (a 2-element array).
        let pair: js_sys::Array = value
            .dyn_into()
            .map_err(|_| Error::fs("entries", "", "entry value not an array"))?;
        let name = pair
            .get(0)
            .as_string()
            .ok_or_else(|| Error::fs("entries", "", "entry[0] not a string"))?;
        let handle_val = pair.get(1);
        let handle: FileSystemHandle = handle_val
            .dyn_into()
            .map_err(|_| Error::fs("entries", "", "entry[1] not a FileSystemHandle"))?;
        let (kind, size) = match handle.kind() {
            FileSystemHandleKind::File => {
                let fh: FileSystemFileHandle = handle.unchecked_into();
                let file_val = JsFuture::from(fh.get_file())
                    .await
                    .map_err(|e| Error::fs("getFile", "", format!("getFile: {}", js_err(&e))))?;
                let file: File = file_val
                    .dyn_into()
                    .map_err(|_| Error::fs("getFile", "", "getFile: not a File"))?;
                (EntryKind::File, Some(file.size() as u64))
            }
            FileSystemHandleKind::Directory => (EntryKind::Directory, None),
            _ => (EntryKind::Other, None),
        };
        out.push(DirEntry { name, kind, size });
    }
    Ok(out)
}

/// Recursive depth-first walk. `depth` is the depth of `dir` relative
/// to the walk root (root itself is depth 0).
async fn walk_dir(
    dir: &FileSystemDirectoryHandle,
    prefix: &str,
    depth: usize,
    max_depth: Option<usize>,
    out: &mut Vec<WalkEntry>,
) -> Result<()> {
    if let Some(d) = max_depth {
        if depth > d {
            return Ok(());
        }
    }
    let entries = collect_entries(dir).await?;
    for entry in entries {
        // Stop once the global cap is hit (an over-large tree must not
        // exhaust memory) — matches NativeFilesystem's MAX_WALK_ENTRIES.
        if out.len() >= MAX_WALK_ENTRIES {
            return Ok(());
        }
        let path = if prefix.is_empty() || prefix == "/" {
            entry.name.clone()
        } else {
            format!("{}/{}", prefix.trim_end_matches('/'), entry.name)
        };
        match entry.kind {
            EntryKind::File => {
                out.push(WalkEntry {
                    path,
                    kind: EntryKind::File,
                    size: entry.size,
                });
            }
            EntryKind::Directory => {
                out.push(WalkEntry {
                    path: path.clone(),
                    kind: EntryKind::Directory,
                    size: None,
                });
                let sub = get_subdir(dir, &entry.name, false).await?;
                // Recursive async — use Box::pin to avoid infinite future size.
                Box::pin(walk_dir(&sub, &path, depth + 1, max_depth, out)).await?;
            }
            _ => {
                out.push(WalkEntry {
                    path,
                    kind: entry.kind,
                    size: entry.size,
                });
            }
        }
    }
    Ok(())
}

/// Best-effort stringify of a JsValue error.
fn js_err(e: &JsValue) -> String {
    if let Some(s) = e.as_string() {
        return s;
    }
    if let Ok(name) = Reflect::get(e, &JsValue::from_str("name")) {
        if let Ok(msg) = Reflect::get(e, &JsValue::from_str("message")) {
            return format!(
                "{}: {}",
                name.as_string().unwrap_or_default(),
                msg.as_string().unwrap_or_default()
            );
        }
    }
    // Fall back to the Object.prototype.toString form.
    let obj: Object = e.clone().unchecked_into();
    obj.to_string().as_string().unwrap_or_else(|| "<js error>".into())
}